A novel signal transduction pathway regulating cell separation processes in plants - the IDA/IDL network and their predicted partners.

Signaling mediated by small peptides is important in cell-to-cell communication. Few peptide ligands involved in cell signaling are known from plants and even less is known about the peptide-ligand-receptor pairs. A group of small putative peptide-ligands have recently been characterized by the Aalen lab. Based on current knowledge these peptides are involved in cell separation processes and mutants have corrupted floral abscission. The few known plant ligands all seem to bind to receptors that possess i ntrinsic kinase activity and there is mounting evidence that some of them are associated with small GTPase binding proteins transducing signals and initiating novel gene expression. In this project we will investigate the signaling circle of a novel class of small peptides involved in abscission and related processes in the model plant Arabidopsis thaliana. The INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) protein and five IDA-LIKE (IDL) proteins have been suggested to act as peptide ligands. We aim at iden tifying their biological function, the genetic pathways they are involved in, their downstream signaling cascade and their influence on gene expression. The two collaborating groups have complementary expertise which makes it possible to enter a more holi stic study of the signal transduction module. Aalen group has for some time been studying the genetic and developmental control of floral abscission and have identified a family of small peptides that may act as ligands while the Bones group has studied t he genetics and molecular function of the RAC/ROP GTPases, interacting partners and their role in intracellular transport. Both groups have used a genetic approach, but in addition Boneslab has expertise in transcriptional profiling, bioinformatics and in tracellular transport, and Aalen lab has expertise in protein-protein interaction studies. The project will take advantage of the expertise and services of the Norwegian Arabidopsis Research Center.